In manufacturing processes of a circuit board, after forming a circuit wiring (electrically conductive pattern) on a board, it is required to inspect the presence of defects, such as disconnection or short-circuit, in the circuit wiring.
As for such an inspection technique, a contact type inspection technique has heretofore been known in which a circuit wiring was subjected to a continuity check or the like by bringing two separate pins into contact with the opposed ends of the circuit wiring to apply an inspection signal (electric signal) from one of the two pins to the circuit wiring ant then receive the inspection signal through the other pin.
However, recent progressive densification in the conductive pattern makes it difficult to assure a sufficient space for bringing the pins into contact with the circuit wiring accurately and simultaneously. Thus, a non-contact type inspection method has been proposed in which the inspection signal was received at the receiving end without using any pin and contacting the circuit wiring.
In this non-contact type inspection technique, any potential disconnection or the like in a circuit wiring is inspected by bringing a pin into contact with one of the ends of the circuit wiring subject to inspection with placing a sensor close to the other end of the circuit wiring, and then supplying a temporally variable inspection signal to the pin to detect a signal appearing at the sensor through a capacitance interposed between the circuit wiring and the sensor.
This technique can achieve the inspection by bringing a pin into contact with only one end of the circuit wiring. Thus, in particular, this technique advantageously makes it possible to inspect a fine circuit wiring.
However, in any conventional inspection techniques, it is essential to bring at least one pin into contact with a circuit wiring to supply an inspection signal. This means that such techniques are unavailable if a circuit wiring is so fine as to preclude the pin from bringing into contact therewith. Further, extremely fine conductive objects such as fragments of a conductive pattern attached on a circuit board as dusts during manufacturing processes of the circuit board or the like cannot be practically inspected by such techniques because such objects cannot be visually distinguished.
It is therefore an object of the present invention to provide an inspection apparatus and inspection method capable of eliminating the need for any pin to be brought into contact with a circuit wiring when supplying an inspection signal to the circuit wiring and capable of detecting any invisible microscopic defects.